The present invention is broadly directed to the preparation of mixed organic-inorganic single phase solids from a polymerizable organic compound which is a solvent for a metallopolymer. More specifically, this invention produces near monodisperse nano-size metallopolymers in an organic polymer host by polymerization with a solubilizing monomer-solvent medium. As used herein, a "metallopolymer" is an inorganic macromolecular complex having only metal-metal bonds in a repeat unit. Preferably the metallopolymer after dissolution has a minimum length of about 15 .ANG.. As such, a metallopolymer generally displays a nanowire or a molecular wire morphology. A metallopolymer is to be distinguished from a metal cluster, a cage compound in which metal atoms are held together by bridging ligands, typically organic, and from simple organometalic compounds not containing metal-metal bonds. "Single phase" refers to a substantially homogeneous dispersion of dissolved portions of the metallopolymers dispersed throughout a matrix of a polymerized organic solvent. The presence of a single phase may be confirmed by conventional techniques such as scanning transmission electron microscopy (STEM) and scanning electron microscope (SEM) analyses.
Substantial research efforts are being focused on the design and fabrication of organic materials containing metallopolymers because of expected applications of such materials in the fields of nanoscale electronic, optical, and mechanical devices. Useful properties exhibited by these materials include anisotropic conductivity, magnetism, size dependent light absorption, and dichroism. A major problem in the preparation of such materials is the prevention of both phase separation and aggregation of the metallopolymers within a host matrix. Nanofibrillar structures have been restricted to the porous confines of a template host from which they have been prepared. In some cases they may be extracted in the form of multifibrillar arrays. (Whitney et al., Science, 261, 1316-19 (1993)) Strategies attempted heretofore to control aggregation, size and morphology have included casting molten metals in zeolite cavities and tensile drawing of bulk metals. Neither of these have enabled the preparation of the products of this invention.
Vassiliou et al., (Preparation of a Novel Polymer Blend of Poly(ethylene oxide) and the Inorganic Polymer (Mo.sub.3 Se.sub.3.sup.-).sub..infin. : Infrared Absorption of Thin Films, 2 Chem. Mater. (1990) pp. 738-741) teach the dispersion of inorganic polymers in an organic solvent which is then evaporated to prepare multi-phase polymer blends of LiMo.sub.3 Se.sub.3 and polyethylene oxide. Vassilou, however, mixes its metal polymers in polymer solutions, not in monomer solutions with subsequent polymerization as in the present invention. Similarly, U.S. Pat. No. 4,546,145 teaches the dispersion of an inorganic substance into a non-solvent monomer, i.e. one having no capacity to function as a solvent whatsoever, to prepare multiphase materials. U.S. Pat. No. 4,871,790 discloses the use of a non-polymerizable organic liquid to prepare a multiphase material.
U.S. Pat. No. 4,297,267 (Leatherman) discloses dissolving a simple hexavalent chromium compound in a liquid diol bis(allyl carbonate) polymerizable solvent to form after polymerization of the liquid diol optically clear colored lenses and the like. Leatherman is limited to the use of non-polymeric hexavalent chromium compounds. U.S. Pat. No. 4,471,078 (Ida) discloses the preparation of selective light absorptive methacrylate resins by adding simple low molecular weight neodynium compounds (about 573 daltons) to a resin-forming methacrylic starting material and then polymerizing the methacrylic monomer. Neither patent discloses anything about metallopolymers which have metal to metal bonds in the repeat unit.
U.S. Pat. No. 4,172,101 (Getson) discloses the preparation of modified organopolysiloxane compositions from organic monomers in the presence of vinyl containing organo polysiloxanes. Similarly, U.S. Pat. No. 5,264,278 (Mazurek) discloses combining a silicone polymer with a polymerizable organic monomer and then polymerizing the mixture into an adhesive layer. Neither of the polymers is a metallopolymer.
Single phase solids with homogeneously distributed metallopolymers have been found to exhibit unexpected properties that have not been found in conventional materials. The polymer host matrix provides sheathing for the metal "wires" and thus protection from environmental degradation while the metal wires enable the composite final product to be useful in optical and electronic environments, especially on the quantum level, which could lead to new nanoscale devices, antistatic coatings, and light polarizers.
Accordingly, it is an object of the present invention to prepare solutions of polymerizable organic solvents and metallopolymers having metal to metal bonds in each repeat unit.
It is a further object to polymerize the solutions so as to prepare single phase solid materials which contain said metallopolymers homogeneously mixed throughout an organic polymer formed in situ from the polymerizable organic solvent.